Subcritical water treatment to modify insoluble dietary fibers from brewer’s spent grain for improved functionality and gut fermentability

Authors: SU, XUEQIAN - Virginia Polytechnic Institution & State University; JIN, QING - University Of Maine; Xu, Yixiang; WANG, HENGJIAN - Virginia Polytechnic Institution & State University; HUANG, HAIBO - Virginia Polytechnic Institution & State University

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2023
Publication Date: 10/4/2023
Citation: Su, X., Jin, Q., Xu, Y., Wang, H., Huang, H. 2024. Subcritical water treatment to modify insoluble dietary fibers from brewer’s spent grain for improved functionality and gut fermentability. Food Chemistry. 435. Article 137654. https://doi.org/10.1016/j.foodchem.2023.137654.
DOI: https://doi.org/10.1016/j.foodchem.2023.137654

Interpretive Summary: Brewer’s spent grain (BSG), the primary by-product in beer production, accounts for 85% of the solid waste generated in the beer brewing process. It is rich in insoluble dietary fiber (IDF, 40–60% dry basis). The rigid and compact structure of BSG-derived IDF presents a significant barrier to gut microbiota. Subcritical water treatment (SWT) has been shown promising modification effects on IDF. This study aims to maximize the BSG valorization by applying lactic acid (LA)-assisted SWT to modify the structure of BSG-derived IDF for its improved functionalities and fermentability as a functional food ingredient. The results indicate that the LA-assisted SWT substantially alters the physiochemical properties of BSG-derived IDF, improving its functionality (e.g., water and oil holding capacity), and enhancing its fermentability and short chain fatty acid production. The results provide a compelling rationale for the valorization of IDF from BSG as a functional food and nutraceutical ingredient, enhancing the sustainability of the brewing industry.

Technical Abstract: Lactic acid (LA)-assisted subcritical water treatment (SWT) was applied to modify the structure of insoluble dietary fiber (IDF) from brewer’s spent grain (BSG) for its better valorization. Characterization was conducted through composition and functionality analysis, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Increasing LA concentration and treatment temperature led to a significant reduction in hemicellulose content in IDF samples from 38.36% to 0.67%, accompanied by the decreased yield (84.8% to 51.4%) and reduced particle size (519.8 µm to 288.6 µm). However, the modified IDF demonstrated improved functionalities, characterized by more porous structures, higher crystalline indices, and enhanced transmittance intensities of characteristic lignin bands. Notably, the modified IDF exhibited slower in-vitro fermentation, promoting the generation of beneficial short-chain fatty acids in the distal colon, while mitigating flatulence during digestion. These findings highlight the potential of LA-assisted SWT in transforming BSG-derived IDF into a valuable functional food ingredient.